One of those who ascertained new, relevant facts was, surprisingly, Liebig himself who in a masterly study, carried out jointly with Wöhler, on the decomposition of amygdalin into oil of bitter almonds and sugar by an apparently protein-like substance occurring in almonds which they termed emulsin, established a typical case of a very extensive series of catalytic phenomena, i.e. enzyme actions.

M. Paul Bert, in his remarkable studies on the influence of barometric pressure on the phenomena of life, has recognized the fact that compressed oxygen is fatal to certain ferments, whilst under similar conditions it does not interfere with the action of those substances classed under the name of SOLUBLE FERM.NTS, such as diastase (the ferment which inverts cane sugar) emulsin and others.

Mitscherlich, more especially, have shown that yeast imparts to water a soluble material, which liquefies cane-sugar and produces inversion in it by causing it to take up the elements of water, just as diastase behaves to starch or emulsin to amygdalin.

We know that Liebig regarded yeast, and, generally speaking, any ferment whatever, as being a nitrogenous, albuminous substance which, in the same way as emulsin, for example, possesses the power of bringing about certain chemical decompositions.